The present invention relates to an apparatus for treating waste water. Specifically, the present invention relates an apparatus which, when waste water discharged from various industrial plants is treated using a solid catalyst and/or a solid adsorbent (hereinafter, simply referred to as xe2x80x9ca solid catalystxe2x80x9d in some cases), effectively prevents the movements of the solid catalyst such as travelling and swinging to solve the problems including the abrasion of the solid catalyst due to the movements, the deterioration of performance thereof, and an increase in pressure loss thereof, thereby treating waste water in a stable manner for a long period of time.
Waste water, discharged from various industrial plants such as chemical plants, food processing plants, metal processing plants, plating plants, printing plate making plants, and photographic processing plants, has been purified through a method such as a wet-oxidation method, a wet-decomposition method, an ozone-oxidation method, and a peroxide-oxidation method.
In a wet-oxidation method using a reaction tower filled with a solid catalyst for example, in general, waste water and an oxygen-containing gas are introduced into the reaction tower, and are allowed to pass through the solid catalyst packed bed from its bottom, so that the waste water is purified. When a waste water and an oxygen-containing gas are introduced into the solid catalyst packed bed, the movement of the solid catalyst such as travelling and swinging easily occurs. Such a movement inevitably creates a problem such as the abrasion of the solid catalyst, the deterioration of the performance thereof, and an increase of the pressure loss. In particular, when waste water and/or an oxygen-containing gas are allowed to pass through the solid catalyst packed bed at high flow rate in order to increase the treatment efficiency, the abrasion of the solid catalyst becomes large.
The above-described problems arise not only in a wet-oxidation method, but also in other methods including a wet-decomposing method and an ozone-oxidation method as well. In a wet-oxidation method, waste water and an oxygen-containing gas, or only an oxygen-containing gas in some cases, are usually allowed to pass through the solid catalyst packed bed from the bottom thereof. In contrast, in the methods other than the wet-oxidation method, what to introduce into the reaction tower, i.e. only waste water, waste water and gas, or only gas, varies by each method (in this case, the kind of gas used depends on each method.). In the following description, for convenience, xe2x80x9cwaste water etc.,xe2x80x9d or simply xe2x80x9cwaste waterxe2x80x9d is used as a term representing xe2x80x9cwaste water and an oxygen-containing gasxe2x80x9d, xe2x80x9cwaste water and a gasxe2x80x9d, xe2x80x9cwaste water onlyxe2x80x9d, xe2x80x9ca gas onlyxe2x80x9d, and xe2x80x9can oxygen-containing gas onlyxe2x80x9d, which are introduced into a solid catalyst packed bed from the bottom thereof.
In order to solve the above-described problems, there has been employed a method in which a fixed pressure member is provided onto the surface of the solid catalyst packed bed. The fixed pressure member, which may be a cover constituted by wire netting, a single-hole or perforated plate, or a grid, presses the solid catalyst from the above so as to prevent its movement.
As a matter of course, there is a case in which nothing is provided onto the solid catalyst packed layer. In this case, however, there is a disadvantage as follows. That is, since no pressure member for preventing the movement of the solid catalyst is provided onto the solid catalyst packed layer, the solid catalyst vigorously moves. Due to the vigorous movement, the problems of the abrasion of the solid catalyst, the deterioration of performance thereof, and an increase in pressure loss become serious. This disadvantage makes it impossible to treat waste water in a stable manner for a long period of time.
For the above reason, in many cases, a fixed pressure member is provided onto a solid catalyst packed bed.
However, when a fixed pressure member, which may be a cover constituted by a wire netting, a single-hole or perforated plate, or a grid, is provided on the solid catalyst packed bed, a problem arises as follows. That is, at the initial stage of waste water treatment, there is no space between the top surface of the solid catalyst packed bed and the bottom surface of the pressure member, and the solid catalyst is properly pressed from the above by the pressure member. However, as the time elapses and the waste water treatment proceeds, it is inevitable that the solid catalyst is compacted in the packed bed or is abraded to lose its volume. The top surface of the solid catalyst packed bed sinks downward, and a space is created between the top surface of the solid catalyst packed bed and the bottom surface of the pressure member. As a result, the solid catalyst vigorously moves, and problems such as the abrasion of solid catalyst, the deterioration of performance thereof, and an increase of pressure loss tend to arise. For this reason, there is a difficulty with the use of a conventional fixed pressure member in treating waste water in a stable manner for a long period of time. Furthermore, when waste water is treated in a reaction tower with a large inner diameter, the use of a conventional fixed pressure member may cause the above-described problems in a short time from the initiation of the waste water treatment.
In addition, in an apparatus in which waste water is introduced into a reaction tower through a nozzle, or a hole of a single-hole or perforated plate and then is discharged from the upper part thereof, there is a disadvantage. That is, the waste water blows off from the nozzle or the hole and strongly collides with the solid catalyst. With the collision of the waste water, the solid catalyst is abraded, and various problems arise with the elapse of time as follows. First, the solid catalyst packed into the reaction tower decreases its volume, and as a result, the performance of the solid catalyst is deteriorated, and the waste water treatment efficiency is lowered. Second, the solid catalyst is abraded, and powder thereof is generated. The powder enters and clogs the space between the solid catalyst particles through which waste water is to flow. As a result, pressure loss increases. Third, a space is created at the bottom area of the solid catalyst packed bed, and with the presence of the space, the solid catalyst easily swings or travels. As a result, the solid catalyst particles collide with each other, and the abrasion thereof is further promoted.
When waste water is treated using a solid catalyst as is the case of the wet-oxidation method described above, instead of charging a solid catalyst directly in a reaction tower, a wire netting is provided at the bottom of a reaction tower and a solid catalyst is charged on the wire netting. There are also cases where, instead of a wire netting, a single-hole or perforated plate or a grid is provided, or alternatively, such a plate or a grid is used together with a wire netting. A wire netting and the like is provided at the bottom of a reaction tower in order to prevent the waste water introduced into the reaction tower from drifting and to allow it to flow uniformly, thereby increasing the treatment efficiency.
However, if the waste water is blown off from the nozzle, or the hole of a single-hole or perforated plate at high linear velocity, the use of the wire netting, the perforated plate, or the grid described is not effective. This problem is especially serious in the case where waste water is treated using gas, in particular in a wet-oxidation method where waste water is treated using a solid catalyst. In such a situation, there has conventionally been difficulty in enhancing the treatment efficiency at increasing the flow rate of the waste water.
The present inventors have conducted studies to find out a method and an apparatus using the method, capable of effectively preventing an abrasion of the solid catalyst, specifically: (1) an abrasion caused by the movement of the solid catalyst in the solid catalyst packed layer; and (2) an abrasion caused by the collision between the solid catalyst and the waste water at the bottom of the solid catalyst packed bed, thereby solving the problems of deterioration of performance of the solid catalyst, deterioration of treatment efficiency, and an increase in pressure loss thereby treating waste water for a long period of time.
As to the abrasion (1), the present inventors have conducted studied on a pressure member capable of following up the sinking of the solid catalyst packed bed, instead of a conventional fixed pressure member. As a result, they have found that it is effective to use different type of a pressure member in accordance with an inner diameter of a reaction tower. That is, when the reaction tower has an inner diameter of about less than 100 mm, and about less than 300 mm at the maximum, it is effective to provide a pressure layer having an ability of following up the movement of the surface of the solid catalyst packed bed thereon (for example, the pressure member is constituted by metal in the form of a stick, an agglomerate, or a column. Its surface coming into contact with the top surface of the solid catalyst packed bed is constituted by wire netting, plate, and the like. The pressure layer has such a size as to just fit inside the reaction tower). Contrary to this, when the reaction tower has a large inner diameter, specifically, 100 mm or larger, 300 mm or larger, and still 600 mm or larger, it is effective to provide a water-permeable pressure layer having an ability of following up the deformation of the solid catalyst packed bed thereon (for example, the pressure layer is capable of deforming so as to sufficiently follow up the deformation of the top surface of the packed bed such as sinking, thereby substantially preventing the creation of a space between the pressure layer and the top surface of the packed bed. The pressure layer is a packed bed of substance in the form of, for example, a sphere, a pellet, and the like.).
When the reaction tower has far larger inner diameter, specifically 350 mm or larger, and still 510 mm or larger, the above-described problem (1) can be effectively solved by providing a partition for dividing the packed bed as the pressure layer into a plurality of segments in a vertical direction.
As to the abrasion (2), that is, an abrasion of the solid catalyst caused by the collision with the waste water introduced from the bottom of the reaction tower, the present inventors have found that it is effective to provide a layer capable of dispersing and mitigating the upward stream of the waste water under the solid catalyst packed bed. The layer is, for example, a packed bed of metal or ceramics.
The present invention has solved the above-described problems, and provides an apparatus having a structure in which a pressure layer capable of following up the deformation or movement of a surface of a packed bed of a solid catalyst and/or a solid adsorbent is provided on the packed bed (there are some cases where the pressure layer is referred to as xe2x80x9can upper packed bedxe2x80x9d.).
Specifically, according to the first embodiment of the present invention which has solved the above-described problems (i.e. a first configuration), a water-permeable pressure layer having an ability of following up the deformation of the top surface of the packed bed of the solid catalyst and/or the solid adsorbent is provided on the packed bed (The water-permeable pressure layer is an example of the above-described xe2x80x9cupper packed bedxe2x80x9d. In order to specify the water-permeable pressure layer among various examples of the upper packed bed, there are some cases where the water-permeable pressure layer is referred to as xe2x80x9can upper deformation packed bedxe2x80x9d.).
According to the second embodiment of the apparatus of the present invention (a second configuration), the above-described upper deformation packed bed is provided on the packed bed of the solid catalyst and/or the solid adsorbent, in addition, the upper part of the solid catalyst packed bed and the upper deformation packed bed are divided into a plurality of segments by a partition in a vertical direction.
According to the third embodiment of the apparatus of the present invention (a third configuration), a layer for dispersing and mitigating the upward stream of waste water and/or gas (hereinafter, simply referred to as xe2x80x9cwaste waterxe2x80x9d again.) is provided under the packed bed of the solid catalyst and/or the solid adsorbent (there are some cases where the dispersing and mitigating layer is referred to as xe2x80x9ca lower packed bedxe2x80x9d.).
According to the fourth configuration of the present invention, the lower packed bed is provided under the packed bed of the solid catalyst and/or the solid adsorbent, in addition, the upper deformation packed bed is provided on the packed bed of the solid catalyst and/or the solid adsorbent. The present invention also includes the fifth configuration in which the fourth apparatus is further provided with a partition for dividing the upper part of the solid catalyst packed bed and the upper deformation packed bed into a plurality of segments in a vertical direction.
According to a sixth embodiment of the apparatus of the present invention which has solved the above-described problems (a sixth configuration), a pressure layer having an ability of following up the movement of the packed bed of the solid catalyst and/or the solid adsorbent (the pressure layer is an example of the above-described xe2x80x9cupper deformation packed bedxe2x80x9d. In order to distinguish the pressure layer from the upper deformation packed bed in the first configuration, there are some cases where the pressure layer is referred to as xe2x80x9can upper movement packed bedxe2x80x9d.).
The present invention also includes the seventh configuration in which the upper movement packed bed is provided on the packed bed of the solid catalyst and/or the solid adsorbent, in addition, the lower packed bed is provided under the packed bed of the solid catalyst and/or the solid adsorbent.